Process for the preparation of diphenylmethane diamines



United States Patent 3,274,247 PROCESS FOR THE PREPARATION OF DDHENYLMETHANE DIAMINES Marcel Repper, Le Clou, Melle, France, assignor to Societe Toulousaine de Produits Chimiques Tolochimie, Paris, France, a corporation of France N0 Drawing. Filed June 14, 1963, Ser. No. 287,779 Claims priority, application France, July 5, 1962, 903,087 3 Claims. (Cl. 260570) This invention relates to a process for the product-ion of phenyl substituted and unsubstituted diphenylmethane diamines, including N-alkylated diamines. It is known that salts of aromatic amines such as aniline hydrochloride react with formaldehyde to produce the corresponding salts of aromatic diamines of the diphenylmethane series. Aniline hydrochloride for example, condenses with formaldehyde to produce 4,4'-diamino diphenylmethane hydrochloride. In such processes, the best yields are obtained by employing a large excess of the amine salt, which excess may be as high as ten moles of amine salt per mole of formaldehyde.

Since the amine is reacted in the form of an acid salt, the process requires not only acid in amount equivalent to the large excess of amine, but also the product and unreacted amine in the form of acid salts must be neutralized by an equivalent amount of base.

An object of the present invention is to improve the above process so as to enable great reductions in the quantities of acid and base employed.

The invention, accordingly, comprises the novel processes and steps of processes specific embodiments of which are described herein by way of example and in accordance with which I now prefer to practice the invention.

I have found in accordance with this invention, that it is possible to condense formaldehyde with phenyl amines in the presence of an acid using an excess of the amine and a low proportion of acid while yet obtaining entirely satisfactory yields. The amines are converted to the corresponding diphenylmethane diamines using a quantity of acid which is below that theoretically required to convert all of the amine to its acid salt.

The phenyl group of the amines employed in the practice of this invention may be substituted or unsubstituted provided, however, that the substituent does not interfere with the reaction. Typical substituents which are mentioned by way of example include one or more halogens, and one or more alkyl or alkoxy groups. Alkoxy substituents may contain up to six carbon atoms and alkyl substituents up to 12 carbon atoms. The ortho or para position on the phenyl nucleus must be unsubstituted in order for the reaction to take place. Best results are obtained if the para position is unsubstituted so that condensation takes place at this position. The nitrogen atom of the amines employed in carrying out the process of this invention may be substituted with one or two alkyl groups containing up to 12 carbon atoms and these may be the same or different.

In practice, the quantity of acid used can be as low as one equivalent per mole of formaldehyde. As little as 0.1 acid equivalent per mole of formaldehyde is effective. The preferred quantity is from 0.15 to 0.5 equivalent. Accordingly, the cost of the process is substantially decreased by reason of the lesser amounts of acid and base employed.

The process may be advantageously carried out utilizing an extremely high molar excess of amine. In practice, however, it is generally not practical to employ more than six moles of amine per mole of formaldehyde.

The rate of reaction in the prior art process referred to above is not substantially affected by increased tem- 3,274,247 Patented Sept. 20, 1966 "Ice perature. I have found most surprisingly that increase in temperature does increase the rate of reaction in the process of this invention. Best results are obtained at a reaction temperature of approximately C. to C. The reaction products, however, are obtained although at a substantially decreased rate at much lower temperatures, so that if desired, the reaction can be carried out for example at :a temperature as low as 50 C.

The process of my invention is carried out by adding the selected acid to the amine in a reaction vessel equipped for agitation. Aqueous formaldehyde, preferably a standard commercial formaldehyde preparation containing from 27% to 40% formaldehyde in water is added while preferably maintaining the temperature in the range of from 15 to 50 C. The rate at which the formaldehyde is added to the reaction mixture is not critical but best yields are obtained if the addition is effected over the shortest possible time. After the addition of the for maldehyde, the mixture is heated to at least 50 C. and preferably maintained at approximately 50 to 100 C. with constant stirring for from about 1.5 to about 5 hours.

The acid employed in the process of the invention may be organic or inorganic. Best results are obtained with strong inorganic acids such as perchloric, sulfuric and hydrochloric. Acetic acid is an example of the organic acids which may be utilized in the process of this inven tion.

The reaction may also be carried out as a continuous operation for example in a reaction vessel continuously fed with acid, amine and formaldehyde and from which the reaction products are continuously withdrawn. The volume of the reaction vessel should be such that the average reaction time is at least 1.5 hours and preferably between 1.5 and 5 hours or even more.

The following examples show the process as I now prefer to practice it. It is to be understood that these examples are illustrative only and that the invention is not to be considered as restricted thereto except as indicated in the appended claims.

Example I (a) For comparison, I shall first describe an operation carried out in accordance with conventional techniques. Two hundred fifty-nine ml. of 11.6 N hydrochloric acid (i.e. 3 moles of HCl were introduced while stirring in 280 grams (3 moles) of aniline, under nitrogen at 7075 C. After formation of the aniline hydrochloride,

- there was introduced 50 grams of 30% aqueous solution of formaldehyde (i.e. 0.5 moles) at a rate of 70 grams per hour. After the formaldehyde introduction, the reaction was allowed to proceed for 1.75 hours at 75 C. The amines were then liberated by neutralization of the mixture, while still hot, by means of sodium carbonate. The organic layer was washed with water, then recovered by decantation. The excess aniline was distilled off in vacuo of 20 mm. Hg. The product was separated from the higher boiling fractions by distillation and collected between -200 C. at 0.5-1 mm. Hg pressure.

The 4,4-diamino' diphenylmethane produced amounted to 81.2 grams.

The yield was 82% with respect to the formaldehyde converted and 77% with respect to the aniline converted.

(b) In accordance with this invention forty-three and two tenths ml. of 11.6 N hydrochloric acid (i.e. 0.5 mole) were introduced with stirring into 820 grams (3 moles) of aniline. After formation of the acid salt, there was added, within less than 40 seconds, 50 grams of 30% aqueous solution of formaldehyde (i.e. 0.5 mole), at room temperature. Then the reaction mixture was heated at 95 C., with stirring, and was maintained at 95 C. for 2.5 hours. After neutralization and washing as in Examaniline.

ple 1(a), the organic layer was recovered and the desired product was recovered by distillation.

The 4,4'-diamino diphenylmethane produced amounted to 83.2 grams.

The yield was 84% with respect to the formaldehyde and 77% with respect to the aniline.

Example II Twenty-five and eight tenths ml. of 11.6 N hydrochloric acid (i.e. 0.29 mole) were introduced into 280 grams (3 moles) of aniline. After formation of the acid salt, there was introduced within 45 minutes, 0.5 mole of formaldehyde in 30% aqueous solution, at C. Then, the temperature was brought to 100 C. Then, the temperature was brought to 100 C. and this temperature was maintained for two hours, under reflux. After neutralization and washing, the organic layer was recovered and the desired product was separated by distillation;

The 4,4-diamino diphenylmethane produced amounted to 78.5 grams.

The yield was 79.2% with respect to the formaldehyde and 72.5% with respect to the aniline.

Example III Twenty-five and eight tenths ml. of 11.6 N hydrochloric acid were introduced into 280 grams of aniline. After formation of the acid salt, there was introduced within 40 seconds, 50 grams of 30% aqueous solution of formaldehyde, at 15 C. Then the temperature was brought to 100 C. and this temperature was maintained for 2.5 hours under reflux. The desired product was recovered as disclosed in the above examples, and amounted to 81.8 grams.

The yield was 82.6% with respect to the formaldehyde and 75.6% with respect to the aniline.

Example IV Twelve and nine tenths ml. of 11.6 N hydrochloric acid (i.e. 0.145 mole) were introduced into 280 grams of After formation of the acid salt, there was introduced, within 30 seconds, 50 grams of 30% aqueous solution of formaldehyde, at C. Then the temperature was brought to 100 C. and this temperature was maintained for two hours. The organic layer separated after neutralization and Water washing, was freed from the excess aniline by distillation. The desired product was obtained by distillation in vacuo of 0.5-1 mm. Hg and amounted to 79.7 grams.

The yield was 80.5% with respect to the formaldehyde and 71.5% with respect to the aniline.

Example V One hundred ninety-six grams of 6% sulfuric acid (i.e. 0.12 mole) were introduced with stirring, into 280 grams of aniline. After formation of the aniline sulfate, there was introduced Within 50 seconds, 50 grams of 30% aqueous solution of formaldehyde, at 45 C. Then the temperature was brought to 90 C. and this temperature was maintained for 2.5 hours. After neutralization, the organic layer was separated and the excess aniline distilled 01f. The desired product was then recovered by distillation, and amounted to 82 grams.

The yield was 82.8% with respect to the formaldehyde 7 and 73.2% with respect to the aniline.

Example VI Twenty-three and two tenths g. of 65% perchloric acid (i.e. 0.15 mole) were introduced into 372 grams (4 moles) I water washing of the organic layer, the desired product was separated by distillation and amounted to 78.5 grams.

The yield was 79.2% with respect to the formaldehyde and 71.8% with respect to the aniline converted.

Example VII Thirty grams (0.5 mole) of acetic acid were mixed with 186 grams (2 moles) of aniline. After formation of the acetate, there was introduced within 30 seconds, into the mixture maintained at 15 C., 50 grams of 30% aqueous solution of formaldehyde (0.5 mole), then the temperature was brought to 100 C. and this temperature was maintained for 2.5 hours. After neutralization with sodium bicarbonate, the amines were decanted and the desired product was recovered by distillation, and mounted to 71.5 grams.

The yield was 74% with respect to the formaldehyde and 68% with respect to the aniline.

Example VIII Twenty-one and six tenths ml. of 11.6 N hydrochloric acid (i.e. 0.25 mole) were introduced into 3 moles of o-toluidine. After complete absorptition of the hydrochloric acid, there were introduced, within less than one minute, 50 grams of 30% aqueous solution of formaldehyde, at 40 C. Then the temperature was brought to 100 C. and this temperature was maintained for 2.5 hours. After neutralization and Washing, the 3,3'- dimethyl-4,4'-diamino diphenylmethane was recovered by distillation in vacuo and amounted to 83.2 grams.

The yield was 78% with respect to the formaldehyde and 72% with respect to the 'o-toluidine.

Example IX Fifty-three and two tenths ml. of 11.6 N hydrochloric acid (0.5 mole) were introduced into 363 grams (2.965 moles) of 98.8% pure N,N-dimethylaniline. After complete absorption of the acid, there was introduced within 40 seconds, into the mixture maintained at 50 C., 50 grams of 30% aqueous solution of formaldehyde (0.5 mole). Then, the temperature was brought to 100 C. and this temperature was maintained for 2.5 hours. After neutralization and washing, the N,N,N,N-tetramethyl- 4,4-diamino diphenylmethane was recovered from the organic layer by distillation in a vacuo and amounted to 121 grams.

The yield was 95.2% with respect to the formaldehyde and 93.2% with respect to the dimethylaniline.

Example X Twenty-five and eight tenths ml. of 11.6 N hydrochloric acid (0.29 mole) were introduced into 363 grams (2.965 moles) of 98.8% pure N,N-dimethylaniline. After formation of the chloride, there was introduced within 40 seconds, into the mixture maintained at 50 C., 50 grams of 30% aqueous solution of formaldehyde (0.5 mole). Then, the temperature was brought to 100 C. and this temperature was maintained for 2.5 hours. After neutralization and Washing, the tetramethyl diamino diphenylmethane was recovered from the organic layer by distillation in a vacuo and amounted to 116 grams.

The yield was 91.2% with respect to the formaldehyde and 90.9% with respect to the dimethylaniline.

What is claimed is:

1. A process for the production of 4,4'-diamino diphenylmethane which consists essentially of reacting formaldehyde with a molar excess of up to 6 moles of aniline per mole of formaldehyde in the presence of from about 0.15 to about 0.5 equivalent of hydrochloric acid per mole of formaldehyde.

2. A process for the production of 3,3'-dimethyl-4,4'- diamino diphenylmethane which consists'essentially of reacting formaldehyde with a molar excess of up to 6 moles of o-toludine per mole of formaldehyde in the presence of from about 0.15 to about 0.5 equivalent of hydrochloric acid per mole of formaldehyde.

3. A process for the production of N,N,N',N'-tetray1-4, '-diaminq. diphenylmethane which consists es- 5 sentially of reacting formaldehyde with a molar excess of up to 6 moles of N,N-dimethyl aniline with per mole of formaldehyde in the presence of from about 0.15 to about 0.5 equivalent of hydrochloric acid per mole of formaldehyde.

References Cited by the Examiner UNITED STATES PATENTS 1,803,331 5/1931 Kladivko 260--570 2,818,433 12/1957 Erickson 260-570 6 2,93 8,054 5/1960 Demers et a1 260570 2,974,168 3/ 1961 Sharp et al. 260570 FOREIGN PATENTS 10,465 1892 Great Britain. 75,373 5/1894 Germany.

CHARLES B. PARKER, Primary Examiner.

ROBERT V. HINES, Assistant Examiner. 

1. A PROCESS FOR THE PRODUCTION OF 4,4''-DIAMINO DIPHENYLMETHANE WHICH CONSISTS ESSENTIALLY OF REACTING FORMALDEHYDE WITH A MOLAR EXCESS OF UP TO 6 MOLES OF ANILINE PER MOLE OF FORMALDEHYDE IN THE PRESENCE OF FROM ABOUT 0.15 TO ABOUT 0.5 EQUIVALENT OF HYDROCHLORIC ACID PER MOLE OF FORMALDEHYDE. 